The present invention relates to a thermal processing furnace and a fabrication method thereof.
During the fabrication of an object to be processed such as a semiconductor wafer, various thermal processing devices are used in order to subject the object to processes such as oxidation, diffusion, or chemical vapor deposition (CVD). In order to enable such processes, an ordinary thermal processing apparatus is configured of a thermal processing furnace that is a process tube forming a processing chamber for accommodating and storing semiconductor wafers, a heater formed of a heating resistance element provided around the periphery of the process tube, and an insulating material provided around the periphery of the heater, wherein the heating resistance element is arranged on an inner wall surface of the insulating material.
The configuration for a thermal processing apparatus that is capable of providing batch processing, for example, is such that a heater wire provided in a helical form along an inner wall surface of a cylindrical insulating member is used as the heating resistance element, and the interior of the thermal processing furnace is heated thereby to a temperature on the order of 1200.degree. C. A material such as ceramic fibers is used as the insulating material, to absorb radiated and conducted heat, greatly reduce the amount of heat required, and thus enable efficient heating.
One method of arranging a heating resistance element in a insulating member is that disclosed in Japanese Patent Laid-Open Publication No. 60-246582. With this fabrication method, a coiled heater wire is used as the heating resistance element, and, after this heater wire has been covered with a thermally shrunk tube and the pitch at which the thermally shrunk heater wire is arrayed has been fixed, a window mold is wound around a columnar core mold and the heater wire is wound over the top of the window mold.
Next, a mold frame that places a lower mold and an upper mold is assembled in the core mold, and an insulating material in slurry form is poured into the mold frame. After the insulating material has been hardened, mold removal, drying, and sintering steps are performed in sequence, and thus an insulating member in which the thermally shrunk tube is embedded can be obtained, in a state in which the heater wire that has melted the thermally shrunk tube is visible through a radiant heat window in the inner wall surface of the insulating member.
However, the above described fabrication method has problems in that a large number of work steps are required (including covering the heater wire with the thermally shrunk tube; winding the window mold and heater wire around the core mold; assembling and removing the mold frame; and hardening, drying, and sintering the insulating member), the process is not very practicable, and a long time is required for the fabrication. Further, when the heater wire is being formed into the helical shape at the predetermined pitch, there are many areas in which the operators are required to be experienced, and thus it is extremely difficult to obtain a good fabrication accuracy.